Merck said that the review findings of the clinical trials showed that V590 and V591 were generally well tolerated, but the immune responses were inferior to those seen after natural infection and as reported for other Covid-19 vaccines.
The company also plans to shift the research and development focus from the V590 and V591 vaccine candidates to MK-7110 and MK-4482 (molnupiravir).
It also plans to advance clinical programmes and scale-up manufacturing of the two investigational medicines. Molnupiravir is being developed in collaboration with Ridgeback Bio.
Merck and its collaborators plan to publish the results of clinical trials of V590 and V591 in a peer-reviewed journal.
Merck Research Laboratories president Dean Y. Li said: “We are grateful to our collaborators who worked with us on these vaccine candidates and to the volunteers in the trials.
“We are resolute in our commitment to contribute to the global effort to relieve the burden of this pandemic on patients, health care systems and communities.”
The discontinuation will result in a change in the fourth quarter result for last year.
The company further plans to continue SARS-CoV-2/COVID-19 research, besides evaluating the potential of the measles-virus vector and vesicular stomatitis virus vector-based platforms in order to pursue broader pandemic-response capabilities.
As per Merck, its MK-7110, formerly known as CD24Fc, is claimed to be a first-in-class investigational recombinant fusion protein, which can modulate the inflammatory response to SARS-CoV-2 by targeting a novel immune pathway checkpoint.
Interim results from a phase 3 study showed greater than 50% reduction in risk of death or respiratory failure in patients with moderate or severe Covid-19. The full results from the study are expected in the first quarter of this year.
Molnupiravir (MK-4482), which is being developed in collaboration with Ridgeback Bio, is an oral investigational antiviral agent. It is presently in phase 2/3 clinical trials in both the hospital and out-patient settings and are expected to be completed in May this year.